Apparatus and methods for locating an object are known in the art. A missing vehicle locator is described in U.S. Pat. No. 5,418,736 issued to Bird which describes using one or more GPS systems in conjunction with a GPS antenna, a receiver/transmitter, a telephone with associated antennas, and a modem mounted in a vehicle whose position is to be monitored. At such time that the vehicle location is to be determined, a paging request is issued and received by a paging responder within the vehicle. The paging request causes the modem to interrogate the GPS receiver to determine the current position of the vehicle, which is then transmitted via the cellular phone link to notify a vehicle location service center of the current location of the vehicle. Other location determining techniques may use a Loran or a Glonass satellite system.
Another object location system is descried in U.S. Pat. No. 5,576,716 to Sadler for locating lost or stolen property that includes a GPS module, microcomputer, modem and a phone, all of which being installed in the vehicle. The system described regularly and automatically computes the position of the property for transmission via a phone link to a central receiver/transmission station.
It is recognized that signal transmission from relatively “low power” transmitting sources are subject to signal corruption due to noise and static. Extracting an information signal containing noise, wherein the information signal is of the same order of magnitude or even smaller than the noise signal, presents a major hurdle to overcome when attempting to extract the information signal from the noise. In this regard, the present invention provides a new and novel signal extraction technique that accommodates the use of a relatively small, low power and undetectable microtransponder in an object location system.